This invention relates to a tire breaker folding drum and method where a wide breaker ply is applied to a cylindrical drum with the leading and trailing ends spliced together. Then a narrow breaker ply is wrapped around the wide breaker ply and its ends spliced. The exposed overlap edges of the wide breaker ply are then folded up over the narrow breaker ply along the edges of the narrow breaker ply.
Heretofore ply turnups have been made by two bladders positioned at each edge such as those shown in U.S. Pat. No. 4,427,473. In U.S. Pat. No. 5,116,449, a single bladder at each edge has been used with an outboard turnover cage to provide the turnup. In each of these cases, the ply edges are carried by the bladders resulting in an uncertain condition of the ply edges after the turnup is completed.
A breaker forming apparatus without a bladder is also shown in U.S. Pat. No. 4,063,987 where a plurality of folding segments are movable radially and axially without a bladder to fold the edges of the wide breaker ply over the edges of the narrow breaker ply. This apparatus requires radially movable segments to hold the breaker material in place during the folding operation in the event the ply material sticks to the folding segments.
The present invention provides a drum having a plurality of circumferentially spaced apart turnup modules positioned at the edges of the drum. Each of the modules has a nose piece movable axially of the drum from an outer position having the same diameter as the diameter of the drum to an inner position overlapping one of the edges of the drum. A spring-loaded belt is wrapped around the nose piece and supports the wide breaker ply overlap edge when the wide breaker ply is applied. After the narrow breaker ply has been applied, each nose piece is moved to an inner position overlapping the drum edge and carries the wide breaker ply overlap edge over the edge of the narrow breaker, pressing the overlap edge against the narrow breaker ply. After turnup of the wide breaker ply overlap edge, the nose piece is moved axially outward and the belt is peeled off the breaker so as not to distort or stretch the material. The turnup modules are mounted on a plurality of drum segments spaced circumferentially around the drum and are retractable with the segments for removal of the folded breaker package.
In accordance with one aspect of the invention there is provided a method of building a folded breaker on a tire building drum having a plurality of drum folding modules at spaced apart edge positions circumferentially of the drum with each module having a belt with a first belt end fastened to the module and a second belt end fastened to an axially movable nose member comprising:
a. wrapping a wide breaker ply around the drum including the first belt end of each belt fastened to the module and splicing the leading edge and trailing edge together,
b. wrapping a narrow breaker ply having a width less than the width of the wide breaker ply around the wide breaker ply exposing an overlap edge of the wide breaker ply at each edge of the wide breaker ply and splicing the leading edge and trailing edge of the narrow breaker ply, characterized by,
c. folding each overlap edge of said wide beaker ply over each edge of the narrow breaker ply by moving the belt carrying each overlap edge over each edge of the narrow breaker ply by moving the nose member over each the edge of the narrow breaker ply.
In accordance with another aspect of the invention there is provided a tire building drum assembly for folding edges of a wide breaker ply over edges of a narrow breaker ply wrapped around the wide breaker ply comprising a plurality of circumferentially spaced drum segments characterized by a center module mounted on each of the drum segments, a folding module mounted on each of the segments at each end of the center module, each folding module having a nose piece movable axially of the drum from an axially outer position having the same diameter as the diameter of the center module to an axially inner position overlapping the center module, a folding belt wrapped around each nose piece with an axially inner end fastened to the center module and an axially outer end connected to a spring means on the nose piece for maintaining tension in the belt providing a support for an overlap edge of the wide breaker ply in the axially outer position of the nose piece and providing for sliding movement of the belt over the nose piece upon axial movement of the nose piece to the axially inner position for folding each overlap edge of the wide breaker ply over each edge of the narrow breaker ply.